Conventionally, as a thin motor, there is known a thin motor including a roller bearing and a rotation sensor.
FIG. 72 is a sectional view in the axial direction of a conventional thin motor 200.
The thin motor 200 includes, as shown in FIG. 72, a housing inner 220 as a stator, a rotor 12 as a rotor, and a cross roller bearing 14 that is interposed between the rotor 12 and the housing inner 220 and rotatably supports the rotor 12.
The cross roller bearing 14 includes an inner ring 14a and an outer ring 14b. The inner ring 14a fits in the outside edge of the housing inner 220 and is fixed to the housing inner 220 in a state in which the inner ring 14a is pressed in the axial direction by an inner ring clamp 26. The outer ring 14b fits in the inside edge of the rotor 12 and is fixed to the rotor 12 in a state in which the outer ring 14b is pressed in the axial direction by an outer ring clamp 28.
A motor unit 16 that applies rotation torque to the rotor 12 and a resolver 30 as a rotation sensor that detects a rotation angle position of the rotor 12 are provided between the rotor 12 and the housing inner 220.
The resolver 30 includes an annular resolver rotor 18 having an inner circumference decentered with respect to the shaft center of the cross roller bearing 14 and a position detector 20 that is arranged to be opposed to the resolver rotor 18 at a predetermined interval and detects a reluctance change between the resolver rotor 18 and the position detector 20. The resolver rotor 18 is integrally attached to the inside edge of the rotor 12. The position detector 20 is integrally attached to the outside edge of the housing inner 220. The resolver rotor 18 is decentered to change the distance between the resolver rotor 18 and the position detector 20 in the circumferential direction, whereby the reluctance changes according to the position of the resolver rotor 18. Therefore, since a fundamental wave component of the reluctance change is one period per one rotation of the rotor 12, the resolver 30 outputs a resolver signal that changes according to the rotation angle position of the rotor 12.
As a conventional roller bearing device, for example, bearing devices described in Patent Documents 1 to 3 are known. The bearing device described in Patent Document 1 is a bearing device in which preload in the axial direction is applied to fix the inner ring 14a and the outer ring 14b. The bearing device described in Patent Document 2 is a bearing device in which a point of action of a bearing is set on the outside of an output shaft. The bearing device described in Patent Document 3 is a bearing device in which a motor is arranged on the outer circumference of a bearing.    Patent Document 1: JP 2005-69252 A    Patent Document 2: JP 2006-25525 A    Patent Document 3: JP 2002-281720 A
However, in the conventional thin motor 200, when the moment load is applied to the thin motor 200, the thin motor 200 tilts around the cross roller bearing 14 and a gap of the resolver 30 changes. Therefore, there is a problem in that the rotation angle position of the rotor 12 cannot be accurately detected. In particular, since the thin motor 200 tilts around the cross roller bearing 14, the gap change is larger as the resolver 30 is further away from the cross roller bearing 14. Since the thin motor 200 is a thin motor, one cross roller bearing 14 has to receive the moment load. It is difficult to increase rigidity and prevent the gap change by increasing the number of cross roller bearings 14.
Therefore, the present invention has been devised in view of such unsolved problems of the conventional techniques and it is an object of the present invention to provide a roller bearing device suitable for preventing misdetection of a rotation sensor when moment load is applied thereto.